How long do COVID antibodies last? This study says they disappear after about 4 months
A new U.K. study of more than 3,000 health care workers says that coronavirus antibodies decline by half in just under three months and disappear after about four and a half.
The findings suggest people may not be able to depend on antibodies as a form of protection from a second infection, as several studies still aren’t clear about what level of immunity they provide and for how long.
What’s more, antibodies last longer in people who had symptoms and fade quicker in those who never did.
The non-peer reviewed study was published Wednesday in the pre-print server medRxiv.
“These findings could be significant: current studies that are using antibodies to assess how many people have been infected in a population might have missed some who have been infected,” study co-author David Eyre, a professor at the University of Oxford’s Nuffield Department of Population Health, said in a news release.
The study tested 3,217 health care workers from the Oxford University Hospitals NHS Foundation Trust for current infection with the coronavirus and for its antibodies.
Over six months, the researchers measured antibody response in the same people to see how the levels changed over time. A total of 452 employees tested positive for COVID-19.
Antibody levels peaked 24 days after the participants’ initial diagnosis but then fell by half at about the 85-day mark. Antibodies lasted an average of 137 days, or about four and a half months, before fading enough to ring in a negative test result.
The researchers were surprised to learn that antibody levels peaked lower and declined faster in younger adults.
“The longer-lived antibodies in older people of working age are intriguing and not completely explained,” Eyre said. “This is still a new disease and we are learning more and more about it all the time, but longitudinal studies like ours are needed to answer some of these important questions about how long and at what level antibodies last, and the extent to which they protect people from reinfection.”
The team also learned that people of Asian ethnicity reached higher maximum antibody levels than people of other ethnicities.
The new study adds to a handful of others that, collectively, have not found a consistent length of time antibodies remain in the body after coronavirus infection.
A separate non-peer reviewed study published last week by the Imperial College London of more than 365,000 randomly selected people in England found that the number of people with antibodies dropped by about 27% over three months.
In this case, the antibody drops were largest in people over 75 compared to younger adults.
Meanwhile, another peer reviewed study published in October found that coronavirus patients produce antibodies for a “stable” five to seven months, suggesting protection from reinfection for at least that long.
Experts warn much is still unknown about how long antibodies last and how effective they are at protecting people from contracting the virus again.
